藻源性湖泛发生过程CDOM变化对水色的影响

利用Y-型沉积物再悬浮发生装置模拟湖泛发生过程,分析其中有色可溶性有机物(CDOM)的变化特征及其对水色的影响.结果表明,藻类死亡过程消耗大量的氧气,水中溶解氧在短时间内消失殆尽,形成厌氧环境;并同时分解产生大量CDOM,使得水中CDOM显著增多.前期阶段,CDOM浓度随时间一直升高,第6 d时CDOM浓度达到峰值,CDOM在443 nm处的吸收系数a_g(443)为4.48 m^-1.水体黑度值(FeS浓度)呈先增大后减小的趋势,最大值0.35mmol/L同样出现在第6 d,整个过程中,CDOM浓度和黑度值变化趋势一致,a_g(443)与水体黑度呈显著正相关.利用Hydrolight和CIE颜色匹配函数模拟不同梯度的CDOM对水色的影响,发现随a_g(443)增大,水体颜色也逐渐由绿色转为棕色,整体向长波方向移动,水色逐渐变暗.因此,可以认为CDOM浓度变化是引起湖泛水体发黑的重要原因之一,可作为定量监测湖泛强度的指示性参数.     

藻源性湖泛发生过程CDOM变化对水色的影响

利用Y-型沉积物再悬浮发生装置模拟湖泛发生过程,分析其中有色可溶性有机物(CDOM)的变化特征及其对水色的影响.结果表明,藻类死亡过程消耗大量的氧气,水中溶解氧在短时间内消失殆尽,形成厌氧环境;并同时分解产生大量CDOM,使得水中CDOM显著增多.前期阶段,CDOM浓度随时间一直升高,第6 d时CDOM浓度达到峰值,CDOM在443 nm处的吸收系数ag(443)为4.48 m-1.水体黑度值(Fe S浓度)呈先增大后减小的趋势,最大值0.35 mmol/L同样出现在第6 d,整个过程中,CDOM浓度和黑度值变化趋势一致,ag(443)与水体黑度呈显著正相关.利用Hydrolight和CIE颜色匹配函数模拟不同梯度的CDOM对水色的影响,发现随ag(443)增大,水体颜色也逐渐由绿色转为棕色,整体向长波方向移动,水色逐渐变暗.因此,可以认为CDOM浓度变化是引起湖泛水体发黑的重要原因之一,可作为定量监测湖泛强度的指示性参数.     

The effects of soil organic matter on soil water retention and plant water use in a meadow of the Sierra Nevada,CA

Tuolumne Meadows is a groundwater dependent ecosystem in the Sierra Nevada of California, USA, that is threatened by hydrologic impacts that may lead to a substantial loss of organic matter in the soil. In order to provide a scientific basis for management of this type of ecosystem, this paper quantifies the effect of soil organic content on soil water retention and water use by plants. First, we show a substantial dependence of soil water retention on soil organic content by correlating Van Genuchten soil water retention parameters with soil organic content, independent of soil texture. Then, we demonstrate the impact of organic content on plants by simulating the degree to which root water uptake is affected by soil water retention with the use of a physically based numerical model of variably saturated groundwater flow. Our results indicate that the increased water retention by soil organic matter contributes as much as 8.8 cm to transpiration, or 35 additional water‐stress free days, during the dry summer when plants experience increased water stress.     

A study of fecal coliform sources at a coastal site using colored dissolved organic matter (CDOM) as a water source tracer

Optical properties of colored dissolved organic matter (CDOM) were measured as a tracer of polluted waters in a Southern California surf-zone with consistently high levels of fecal indicator bacteria. Salinity, temperature, fecal coliform, absorbance (200-700nm) and fluorescence (lambda(excitation)=350nm; lambda(emission)=360-650nm) were measured in the creek and surf-zone during a dry and rain event. Fluorescence to absorption ratios for CDOM were used to distinguish water masses, with two distinct CDOM end-members identified as creek (flu/abs=8.7+/-0.8x10(4)) and coastal (flu/abs=2.2+/-0.3x10(4)). Waters containing the same CDOM end-member had highly variable bacterial levels during the dry event, suggesting intermittent sources of bacteria added to a uniform water source, consistent with marine birds. During the rain event, increased levels of the creek end-member and bacteria indicated a second bacteria source from runoff.     

Effect of pH on binding of pyrene to hydrophobic fractions of dissolved organic matter(DOM) isolated from lake water

In order to better understand the compositional and structural complexity of dissolved organic matter(DOM) macromolecules and provide mechanistic information on the binding of hydrophobic organic contaminants(HOCs) to DOM, we fractionated large amounts of lake water into three hydrophobic DOM-fractions. The variation of the partitioning coef?cients(K_(DOC)) of pyrene at different p H levels was examined by ?orescence quenching titration. Results show that, relative to the more polar acidic DOM-fractions, the hydrophobic neutral fraction exhibits a higher sorption ability to pyrene. Generally, the sorption of pyrene to the three hydrophobic fractions is strongly pH-dependent. The K_(DOC) values of pyrene generally increase with decreasing p H levels, which is especially obvious in the sorption of pyrene to the fulvic acid fractions, suggesting that the binding is controlled by hydrophobic interactions. The mechanisms underlying the binding of pyrene to the hydrophobic fractions were also discussed. Our data are bene?cial to further understanding the binding of HOCs to DOM and how it has been affected,which may result in more accurate predictions of K_(DOC).     

Simulating methane emission from a Chinese rice field as influenced by fertilizer and water level

Natural and agricultural wetlands are considered to be the major sources of global atmospheric methane (CH₄). A one‐dimensional model was developed to simulate methane emission and used to examine the influence of various physical processes on the rate of methane emission. Three processes involved in the methane emission are implemented in the model: production, reoxidation and transport. Three transport pathways were considered: diffusion across water–air or soil–air interfaces, ebullition and diffusion through plants. These pathways are influenced by soil properties, plant growth, water‐table conditions, temperature and external inputs (e.g. fertilizer). The model was used to examine the seasonal variation of the methane emission at a rice field in Hunan, China, which was observed during a field experiment for consecutive (early and late) rice seasons in 1992. The observed seasonal variations of methane emission, and role of plants in transporting methane to the atmosphere, are captured by the model simulation. Further model applications were conducted to simulate effects of fertilizer and water‐level condition on the methane emission. The results indicate that unfermented organic fertilizer produces a higher methane emission rate than mineral fertilizer. The simulations with treatments of a deep‐water covering and constant moisture reduced the methane emission. The rice field study provides a framework for further development of the model towards simulations based on spatially distributed variables (e.g. water table, soil temperature and vegetation) at a regional scale. Copyright © 2003 John Wiley & Sons, Ltd.     

Impact of natural (storm) and anthropogenic (trawling) sediment resuspension on particulate organic matter in coastal environments

In order to assess the impact of natural and anthropogenic sediment resuspension on quantity, biochemical composition and bioavailability of particulate organic matter (POM), two field investigations were carried out in two shallow coastal areas of the Mediterranean Sea. In the Gulf of Lions, we investigated the impact of a storm resuspension of sediment, whereas in the Thermaikos Gulf we investigated the impact of bottom trawling.Resuspension in the Gulf of Lions determined the increase of sedimentation rates, modified the composition of the organic fraction of settling particles and decreased the labile fraction of POM, as indicated by a drop in the enzymatically hydrolysable amino acid fraction. The increase in the refractory fraction, following short-term storm-induced resuspension, increased also the contribution of glycine and decreased the contribution of aspartic acid contents to the total amino acid pools.Trawling activities in Thermaikos Gulf determined a significant increase in suspended POM concentrations and important changes in its biochemical composition. After trawling, the protein to carbohydrate ratio decreased (as a result of a major input of sedimentary carbohydrates at the water–sediment interface) and the fraction of enzymatically hydrolysable biopolymeric C decreased by ≈30%, thus reducing the bioavailability of resuspended organic particles. Results of the present study indicate that changes in suspended POM, induced by storms and trawling activities, can have similar consequences on benthic systems and on food webs. In fact, the potential benefit of increased organic particle concentration for suspension feeders, is depressed by the shift of suspended food particles towards a more refractory composition.     

1987—2022年新安江水库（千岛湖）水面面积时空变化及其与水位、蓄水量的响应关系

水面面积、水位、蓄水量是水库水资源管理的重要基础数据,遥感是湖库水体提取、水位和蓄水量估算的重要技术手段。由于不同水体提取方法的适用性差异、测高卫星数据的有限时间覆盖度和开源数据集的时空分辨率不足等原因,湖库水面面积、水位、蓄水量的长时序、高频率时空变化监测仍存在一定挑战。本研究以新安江水库为研究区,结合多源遥感、气象、水文和土地利用等数据,基于Google Earth Engine云平台,运用水体指数法,分析1987—2022年新安江水库水面面积时空变化特征,构建水位—水面面积、水位—蓄水量和水面面积—蓄水量响应关系,探究水面面积时空变化成因。结果表明:(1)Landsat 5、Landsat 8和哨兵2号数据的最佳水体提取指数分别为AWEI_sh和GNDWI,F1-score分别为91.93%、91.03%和93.14%。相比于开放数据集GSWED(32.61%)、JRC GSW(76.17%)和ReaLSAT(69.76%),基于最优水体指数的水体提取结果具有最高的F1-score(91.26%);(2)时间上,1987—2022年新安江水库水面面积呈显著上升...     

太湖水体交换周期变化(1986-2018年)及对水质空间格局的影响

针对太湖水体交换周期近十余年发生的变化,本文收集整理了1986-2018年太湖水文巡测、汛期水文巡测数据以及太湖流域沿江城市引水量、流域降雨量变化数据,基于太湖出入湖水量的变化研究了太湖水体交换周期的变化及原因,并对交换周期变化对水质空间格局的影响进行分析.结果 表明:太湖入湖水量有显著上升,2007年以来平均每年入湖...     

Toxicity identification evaluation (TIE) of pore water of contaminated marine sediments collected from Hong Kong waters

Marine sediment can function both as a source and as a sink of marine chemical contaminants. The toxicity of contaminated marine sediment can be assessed by toxic evaluation of its pore water, the inter-particle water of sediment, because toxicants in the pore water may be bioavailable to marine organisms. In this study, the toxicity identification evaluation (TIE) was performed to identify the major toxicants in the pore water of marine sediment collected in Hong Kong waters. In Phase 1 TIE, the suspected toxicants were characterized as anions or organic compounds that are either oxidizable or filterable in alkaline medium. In Phase 2 TIE, the suspected toxicants were identified as sulfide (S²⁻) based on the reduction of toxicity due to lowering of sulfide concentrations by experimental manipulations. The mass balance and spiking analyses in Phase 3 confirmed that S²⁻ was one of the major toxicants and that some non-toxic unknown compounds measured by LC–MS, which was removed by C18 solid phase extraction, enhanced the toxicity of S²⁻ in the pore water samples.     

Geochemical characterization of soil organic matter and variability of a postglacial detrital organic supply (chaillexon lake,france)

Geochemical analysis of sedimentary organic matter in recent lacustrine sediments appears to be a useful tool in providing information concerning past environmental conditions. However, such analysis is often made without knowing the geochemical characteristics of the organic matter derived from the watershed and, more explicitly, its soils. The present work deals with (i) a geochemical investigation (Rock-Eval pyrolysis) of soil organic matter sampled in a lake watershed, and (ii) the study of the sedimentary organic matter trapped in the lake deposits. The research was conducted on Chaillexon Lake which was created by a rock collapse that dammed the palaeovalley of the Doubs River about 12 000 years ago. Since this event, the sediment trap provides a continuous palaeoclimatic record for the Postglacial period. Results obtained lead to two main conclusions. First, the variability of Rock-Eval pyrolysis values observed in soils modifies the common interpretation given to these parameters in the characterization of sedimentary organic matter. Indeed, variations in these parameters point not only to varying proportions of terrestrial and lacustrine organic matter in a lacustrine infilling but also to variations of the terrestrial supply linked with the evolution of vegetal cover in the catchment. The second conclusion is that the story of the Chaillexon lacustrine system is marked by a rather sudden soil and forest development at the Preboreal–Boreal transition (9000 BP ). Copyright © 1998 John Wiley & Sons, Ltd.     

Bioavailability and radiocarbon age of fluvial dissolved organic matter (DOM) from a northern peatland-dominated catchment: effect of land-use change

The radiocarbon age and biodegradability of dissolved organic matter (DOM) from a northern peat-dominated river system was studied and the effects of land-use were compared. Samples were obtained from streams and ditches comprising sub-catchments of the Kiiminki River, Northern Finland. Sample sites included areas of natural mire, areas subjected to moderate disturbance (ditching to enhance forestry), and areas subjected to serious land use change (agriculture and peat excavation). The study employed a 55 day bioassay that measured the biodegradation potential of surface-water DOM. We identified release of modern (mean 6–13 year old) DOM from natural sites, and material aged up to 1,553 years from disturbed sites. The proportion of biodegradable DOC ranged from 4.1 to 17.9 %, and bacterial DOC removal was modelled using twin-pool and reactivity-continuum (beta distribution) approaches. Bacterial growth efficiency ranged from 0.11 to 0.26 between areas of different land use, and these relatively low values reflect the humic-rich DOM released from boreal peatland. Despite the range of land-use types studied, including intensive peatland excavation areas, there was no detectable relationship between the biological lability of DOM and its radiocarbon age.     

煅烧改性净水厂污泥对底泥内源磷释放的控制效果

以自主研发的煅烧改性净水厂污泥（C-WTPS）作为污染底泥活性覆盖材料,室内静态模拟实验研究C-WTPS覆盖强度对控制底泥磷释放效果的影响,分析C-WTPS和底泥中不同形态磷含量变化,探讨C-WTPS薄层覆盖对上覆水体中pH、DO和ORP的影响.结果表明,实验历时40天,在底泥TP释放强度为6.25~10.87 mg/（m²·d）时,覆盖强度为0.25、0.50、1.00、1.50和2.00 kg/m²的C-WTPS对TP平均削减率分别为59.68%、75.71%、88.75%、92.42%和96.28%,可见覆盖强度为1.00 kg/m²以上的C-WTPS能控制底泥中90%以上TP释放.C-WTPS吸附的磷主要以无机磷（IP）中的铁铝结合态磷（NAIP）形式存在,有机磷（OP）和钙磷（AP）形式较少.C-WTPS促进了底泥中易释放形态磷迁移到C-WTPS中,并转化较为稳定的形态磷,可见C-WTP覆盖不仅控制了底泥磷释放,而且也削减了底泥磷释放风险.C-WTPS覆盖后,上覆水体中pH开始呈现下降趋势,最终维持在pH=7范围波动;C-WTPS覆盖强度越大,上覆水体pH下降也明显;C-WTPS覆盖改善上覆水体中DO和ORP环境的效果不明显.     

PAH body burden and biomarker responses in mussels (Mytilus edulis) exposed to produced water from a North Sea oil field: laboratory and field assessments

In order to study the impact of produced water (PW) from a North Sea oil field on blue mussels (Mytilus edulis), chemical and biological markers were selected. A laboratory exposure (0.125%, 0.25% and 0.5% of PW) and a field study (6 stations 0.2-2 km from a PW discharge point) were conducted. In the laboratory study, PAH bioaccumulation increased in mussel soft tissue even at the lowest exposure dose. Micronuclei frequency demonstrated a dose-response pattern, whereas lysosomal membrane stability showed tendency towards a dose-response pattern. The same markers were assessed in the field study, biomarker analyses were consistent with the contamination level, as evaluated by mussel polycyclic aromatic hydrocarbons body burden. Overall, obtained results confirmed the value of an ecotoxicological approach for a scientifically sound characterisation of biological effects induced by offshore oilfield operational discharges.     

有色可溶性有机物(CDOM)吸收作为湖库化学需氧量监测替代指标的探讨

化学需氧量是衡量水体中有机物量及污染程度的综合性指标,也是我国《地表水环境质量标准(GB 3838—2002)》的重要评价指标.然而,由于测定过程缓慢和使用了有毒有害试剂易于形成二次污染,现行标准的高锰酸钾和重铬酸钾化学需氧量测定方法无法做到环境友好,也不能反映当前快速和实时监测的技术需求.因此,迫切需要发展操作简便、快速高效、灵敏可靠、环境友好和环保绿色的化学需氧量替代检测方法.本文首先从文献计量学视角比较我国与世界上发达国家化学需氧量研究主题论文发文量,剖析了我国发展化学需氧量替代检测方法的迫切性.基于全国大范围65个湖库706个样本有色可溶性有机物吸收系数、化学需氧量和其他水质参数同步调查数据,构建广覆盖范围的有色可溶性有机物特征波长吸收系数和化学需氧量间高精度线性关系模型,确定了地表水环境质量评价的吸收系数阈值,模型可以广泛应用于不同类型(深水、浅水、大型、中型、小型)和不同营养状态(贫、中、富营养)湖库水体有机物浓度的定量表征,具有一定普适性.通过对比有色可溶性有机物吸收系数和传统的高锰酸钾、重铬酸钾法优势和不足,明确了有色可溶性有机物吸收系数替代化学需氧量用于湖库水体开展有...     

Trace metal dynamics in the water column and pore waters in a temperate tidal system: response to the fate of algae-derived organic matter

Tidal and seasonal behaviour of the redox-sensitive trace metals Mn, Fe, Mo, U, and V have been investigated in the open-water column and shallow pore waters of the backbarrier tidal flats of the island of Spiekeroog (Southern North Sea) in 2002 and 2007. The purpose was to study the response of trace metal cycles on algae blooms, which are assumed to cause significant changes in the redox state of the entire ecosystem. Trace metal data were complemented by measurements of nutrients and enumeration of algae cells in 2007. Generally, Mn and V show a tidal cyclicity in the water column with maximum values during low tide which is most pronounced in summer due to elevated microbial activity in the sediments. Mo and U behave almost conservatively throughout the year with slightly increasing levels towards high tide. Exceptions are observed for both metals after summer algae blooms. Thus, the seasonal behaviour of the trace metals appear to be significantly influenced by productivity in the water column as the occurrence of algae blooms is associated with an intense release of organic matter (e.g. transparent exopolymer particles, TEP) thereby forming larger organic-rich aggregates. Along with elevated temperatures in summer, the deposition of such aggregates favours microbial activity within the surface sediments and release of DOC, nutrients and trace metals (Mn, Mo and V) during the degradation of the aggregates. Additionally, pronounced reducing conditions lead to the reduction of Mn(IV)-oxides and Fe(III)-(oxihydr)oxides, thereby releasing formerly scavenged compounds as V and phosphate. Therefore, pore-water profiles show significant enrichments in trace metals especially from July to September. Finally, the trace metals are released to the open water column via draining pore waters (esp. Mo, Mn, and V) and/or fixed in the sediment as sulphides (Fe, Mo) and bound to organic matter (U). Non-conservative behaviour of Mo in oxygenated seawater, first observed in the investigation area by Dellwig et al. (Geochim Cosmochim Acta 71:2745–2761, 2007a), was shown to be a recurrent phenomenon which is closely coupled to bacterial activity after the breakdown of algae blooms. In addition to the postulated fixation of Mo in oxygen-depleted micro-zones of the aggregates or by freshly formed organic matter, a direct removal of Mo from the water column by reduced sediment surfaces may also play an important role.